Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds only the backing endpoint (GET /custom-fields); it does not say whether the listing spans all objects by default, whether pagination must be followed, or what a definition record contains.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences, both front-loaded, with the resource and the optional filter stated immediately. The trailing "GET /custom-fields" is modest technical filler but not harmful.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-required-parameter read-only list tool with annotation coverage and an inline-documented pagination scheme in the schema, the description covers what is being returned and the one meaningful filter. No output schema exists, so a brief note on result contents would help, but nothing critical is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 67%: page and limit are documented in the schema, while object_type has only an enum and no description. The description partly compensates by framing object_type as an optional single-object-type filter, but it adds no detail on default behavior when omitted. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("List custom field definitions") plus an optional scope ("for one object type"), which is enough to distinguish it from the many other list_* siblings by resource name alone. It stops short of explicitly contrasting with any alternative, but the resource is unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Optionally for one object type" implies when the filter is relevant, but there is no explicit when-to-use guidance, no stated exclusions, and no mention of when an agent would need custom field definitions at all (e.g. before creating or updating records). Usage is inferable rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.